1994 JEEP WRANGLER brake sensor

energized). This is done to compensate for the re-
duced flow through injector caused by the lowered
voltage.
BRAKE SWITCHÐPCM INPUT
When the brake light switch is activated, the pow-
ertrain control module (PCM) receives an input indi-
cating that the brakes are being applied. After
receiving this input, the PCM maintains idle speed
to a scheduled rpm through control of the idle air
control (IAC) motor. The brake switch input is also
used to operate the speed control system.
CAMSHAFT POSITION SENSORÐPCM INPUT
A sync signal is provided by the camshaft position
sensor located in the ignition distributor (Fig. 5). The
sync signal from this sensor works in conjunction
with the crankshaft position sensor to provide the
powertrain control module (PCM) with inputs. This
is done to establish and maintain correct injector fir-
ing order.
Refer to Camshaft Position Sensor in Group 8D, Ig-
nition System for more information.
DATA LINK CONNECTORÐPCM INPUT
The data link connector (diagnostic scan tool con-
nector) links the DRB scan tool with the powertrain
control module (PCM). The data link connector is lo-
cated in the engine compartment (Figs. 6 or 7). For
operation of the DRB scan tool, refer to the appropri-
ate Powertrain Diagnostic Procedures service man-
ual.
The data link connector uses two different pins on
the PCM. One is for Data Link Transmit and the
other is for Data Link Receive.
INTAKE AIR TEMPERATURE SENSORÐPCM INPUT
The intake manifold air temperature sensor is in-
stalled in the intake manifold with the sensor ele-
ment extending into the air stream (Figs. 8 or 9).
The sensor provides an input voltage to the power-
train control module (PCM) indicating intake mani-
fold air temperature. The input is used along with
inputs from other sensors to determine injector pulse
width. As the temperature of the air-fuel stream in
the manifold varies, the sensor resistance changes.
This results in a different input voltage to the PCM.
CRANKSHAFT POSITION SENSORÐPCM INPUT
This sensor is a Hall Effect device that detects
notches in the flywheel (manual transmission), or
flexplate (automatic transmission).
This sensor is used to indicate to the powertrain
control module (PCM) that a spark and or fuel injec-
tion event is to be required. The output from this
sensor, in conjunction with the camshaft position
sensor signal, is used to differentiate between fuel in-
jection and spark events. It is also used to synchro-
nize the fuel injectors with their respective cylinders.
Fig. 5 Camshaft Position Sensor
Fig. 6 Data Link ConnectorÐYJ ModelsÐTypical
Fig. 7 Data Link ConnectorÐXJ ModelsÐTypical
14 - 20 FUEL SYSTEMJ

(10) Inspect fuel tube quick-connect fitting-to-fuel
rail connections (Fig. 15).
(11) Verify that hose connections to all ports of
vacuum fittings on intake manifold are tight and not
leaking.
(12) Inspect accelerator cable, transmission throt-
tle cable (if equipped) and cruise control cable con-
nections (if equipped). Check their connections to the
throttle arm of throttle body for any binding or re-
strictions (Fig. 16).
(13) If equipped with vacuum brake booster, verify
that vacuum booster hose is firmly connected to fit-
ting on intake manifold. Also check connection to
brake vacuum booster (Fig. 17).
(14) On XJ models equipped with 4.0L engine and
A/C, verify that auxiliary cooling fan wire connector
is firmly connected to harness (Fig. 18).
(15) Inspect the air cleaner inlet and air filter ele-
ment for restrictions.
(16) Inspect radiator grille area, radiator fins and
air conditioning condenser for restrictions.(17) Verify that intake manifold air temperature
sensor wire connector is firmly connected to harness
connector (Figs. 19 or 20).
(18) Inspect engine ground strap connections at
dash panel and rear cylinder head bolt (Fig. 21).
(19) Verify that MAP sensor electrical connector is
firmly connected to MAP sensor (Fig. 22). Verify that
vacuum hose is firmly connected to MAP sensor and
to the intake manifold.
(20) Verify that fuel injector wire harness connec-
tors are firmly connected to the fuel injectors in the
correct order. Each harness connector is tagged with
the number of its corresponding fuel injector (Fig.
23).
Fig. 15 Fuel Supply TubeÐTypical
Fig. 16 Throttle Body CablesÐTypical
Fig. 17 Brake Vacuum Booster HoseÐTypical
Fig. 18 Auxiliary Cooling Fan ConnectorÐXJ with
4.0L Engine
JFUEL SYSTEM 14 - 35

IDLE AIR CONTROL MOTOR TEST
Idle Air Control (IAC) Motor operation can be
tested using special exerciser tool number 7558 (Fig.
42).
CAUTION: Proper safety precautions must be taken
when testing the idle air control motor:
²Set the parking brake and block the drive wheels
²Route all tester cables away from the cooling fans,
drive belt, pulleys and exhaust components
²Provide proper ventilation while operating the en-
gine
²Always return the engine idle speed to normal be-
fore disconnecting the exerciser tool
(1) With the ignition OFF, disconnect the IAC mo-
tor wire connector at throttle body (Fig. 42).
(2) Plug the exerciser tool number 7558 harness
connector into the IAC motor.
(3) Connect the red clip of exerciser tool 7558 to
battery positive terminal. Connect the black clip tonegative battery terminal. The red light on the exer-
ciser tool will flash when the tool is properly con-
nected.
(4) Start engine.
When the switch on the tool is in the HIGH or
LOW position, the light on the tool will flash. This
indicates that voltage pulses are being sent to the
IAC stepper motor.
(5) Move the switch to the HIGH position. The en-
gine speed should increase. Move the switch to the
LOW position. The engine speed should decrease.
(a) If the engine speed changes while using the
exerciser tool, the IAC motor is functioning prop-
erly. Disconnect the exerciser tool and connect the
IAC motor wire connector to the stepper motor.
(b) If the engine speed does not change, turn the
ignition OFF and proceed to step (6). Do not discon-
nect exerciser tool from the IAC motor.
(6) Remove the IAC motor from the throttle body.
Do not remove IAC motor housing from throttle
body.
CAUTION: When checking IAC motor operation with
the motor removed from the throttle body, do not
extend the pintle (Fig. 43) more than 6.35 mm (.250
in). If the pintle is extended more than this amount,
it may separate from the IAC motor. The IAC motor
must be replaced if the pintle separates from the
motor.
(7) With the ignition OFF, cycle the exerciser tool
switch between the HIGH and LOW positions. Ob-
serve the pintle. The pintle should move in-and-out
of the motor.
(a) If the pintle does not move, replace the idle
air control motor. Start the engine and test the re-
placement motor operation as described in step (5).
(b) If the pintle operates properly, check the idle
air control motor bore in the throttle body bore for
blockage and clean as necessary. Reinstall the idle
air control motor and retest. If blockage is not
Fig. 41 Oxygen SensorÐTypical
Fig. 42 IAC Motor TestingÐTypical
Fig. 43 Idle Air Control (IAC) Motor Pintle
14 - 46 FUEL SYSTEMJ

MULTI-PORT FUEL INJECTION (MFI)ÐCOMPONENT REMOVAL/INSTALLATION
INDEX
page page
Accelerator Pedal and Throttle Cable......... 54
Air Cleaner Housing...................... 54
Air Conditioning (A/C) Clutch Relay........... 54
Air Filter............................... 54
Automatic Shut Down (ASD) Relay........... 54
Brake Switch............................ 54
Camshaft Position Sensor.................. 54
Crankshaft Position Sensor................. 55
Engine Coolant Temperature Sensor.......... 55
Fuel Filter.............................. 55
Fuel Injector............................ 55
Fuel Pump Module....................... 56
Fuel Pump Relay........................ 56
Fuel Rail Assembly....................... 56
Fuel System Pressure Release Procedure...... 56
Fuel Tank Pressure Relief/Rollover Valve...... 56
Fuel Tanks............................. 56Fuel Tubes/Lines/Hoses and Clamps.......... 56
Idle Air Control (IAC) Motor................. 56
Ignition Coil............................. 57
Intake Air Temperature Sensor.............. 54
Intake Manifold.......................... 57
Manifold Absolute Pressure (MAP) Sensor..... 57
Oxygen (O2S) Sensor..................... 57
Park Neutral Switch....................... 58
Power Steering Pressure SwitchÐ2.5L
Engine Only........................... 58
Powertrain Control Module (PCM)............ 58
Quick-Connect Fittings..................... 59
Throttle Body............................ 59
Throttle Position Sensor (TPS).............. 59
Torque Converter Clutch Relay.............. 60
Vehicle Speed Sensor..................... 60
ACCELERATOR PEDAL AND THROTTLE CABLE
Refer to the Accelerator Pedal and Throttle Cable
section of this group for removal/installation proce-
dures.
AIR CONDITIONING (A/C) CLUTCH RELAY
The A/C clutch relay is located in the Power Dis-
tribution Center (PDC) (Figs. 1 or 2). For location of
this relay within the PDC, refer to label on PDC
cover.
AIR CLEANER HOUSING
Refer to Group 25, Emission Control System.
AIR FILTER
Refer to Group 25, Emission Control System.
AUTOMATIC SHUT DOWN (ASD) RELAY
The ASD relay is located in the Power Distribution
Center (Figs. 1 or 2) (PDC). For location of this relay
within the PDC, refer to label on PDC cover.
BRAKE SWITCH
Refer to Group 5, Brakes for removal/installation
procedures.
CAMSHAFT POSITION SENSOR
For removal/installation procedures, refer to Group
8D, Ignition System. See Camshaft Position Sensor.
INTAKE AIR TEMPERATURE SENSOR
The intake manifold air temperature sensor is in-
stalled into the intake manifold plenum (Figs. 3 or
4).
Fig. 1 PDCÐYJ Models
Fig. 2 PDCÐXJ Models
14 - 54 FUEL SYSTEMJ

Fig. 6 Wheel Speed Sensors
JBRAKES 5 - 41

Fig. 13 Solenoid Valves In Pressure Increase Cycle
Fig. 14 Pedal Travel Sensor Actuation
JANTILOCK BRAKE SYSTEM OPERATION 5 - 45

Wiring Diagram Name Sheet Number
ABS Accelerator Sensor........................59
ABS Control Module.....................57, 58, 59
ABS Control Module Connector...................60
ABS Motor Pump Relay........................57
ABS Power Relay............................57
A/C Blower Switch............................50
A/C Compressor.............................49
A/C Low Pressure Switch.......................49
A/C Relay.................................49
A/C Thermostat..............................50
Accessory Illumination.........................32
Air Conditioning System (4.0L).................49, 50
A/C Blower Switch..........................50
A/C Compressor............................49
A/C Low Pressure Switch.....................49
A/C Relay................................49
A/C Thermostat............................50
Field Jumper..............................50
Powertrain Control Module.....................49
Anti-Lock Brake System (TEVES).............57, 58, 59
ABS Accelerator Sensor.......................59
ABS Control Module....................57, 58, 59
ABS Motor Pump Relay.......................57
ABS Power Relay...........................57
Brake Pedal Travel Sensor.....................57
Data Link Connector.........................57
Diode..................................58
Hydraulic Actuation Unit......................58
Left Front Wheel Sensor......................59
Left Rear Wheel Sensor.......................59
Power Distribution Center.....................57
Pump Motor..............................57
Pump Motor Sensor.........................57
Right Front Wheel Sensor.....................59
Right Rear Wheel Sensor......................59
Automatic Shut-Down Relay...................11, 17
Back-Up Lamps...........................51, 52
Back-Up Lamp Switch..........................7
Battery................................1,3,5
Blower Motor...............................47
Blower Resistor.............................47
Blower Switch..............................47
Body Harness Connector........................36
Brake Pedal Travel Sensor.......................57
Brake Warning Switch..........................9
Bulkhead Connector........................65, 66
Buzzer Module..............................36
Camshaft Position Sensor....................12, 18
Center High Mounted Stop Lamp..................52
Charging System 2.5L Engine...................3,4
Battery..................................3
Generator.................................3
Power Distribution Center......................4

Wiring Diagram Name Sheet Number
A/C Compressor Clutch Relay...................3,69
A/C Compressor Clutch........................69
A/C Heater Blower Motor.......................70
A/C Low Pressure Switch.......................69
A/C Mode Select Switch........................70
A/C Thermostat..............................69
ABS Diode.................................33
ABS Green Indicator Lamp......................57
ABS Hydraulic Actuation Unit.....................33
ABS #1 Relay.............................3,31
ABS #2 Relay.............................3,31
ABS Pump Motor............................30
ABS Red Indicator Lamp.......................57
Ambient Temperature Sensor.....................53
Antenna...................................71
Antenna Mast...............................71
Anti-Lock Brake Control Module Connector...........109
Anti-Lock Braking System...............29,30,31,32,33
ABS Diode...............................33
ABS Relays...............................31
Anti-Lock Pump Motor.......................30
Anti-Lock Brake System Module.........29,30,31,32,33
Data Link Connector.........................32
G Sensor................................30
Hydraulic Actuation Unit......................33
Left Front Wheel Sensor......................29
Left Rear Wheel Sensor.......................29
Pedal Travel Sensor.........................30
Right Front Wheel Sensor.....................29
Right Rear Wheel Sensor......................29
Anti-Lock Brake System Module...........29,30,31,32,33
Anti-Lock Pump Motor.........................30
Anti-Lock Relay..............................31
Ashtray Lamp...............................48
Automatic Shut Down Relay..................3,12,17
Automatic Transmission Control System (2.5L).........27
Front Axle Lock-Up Switch.....................27
EMCC Relay..............................27
EMCC Solenoid............................27
Back-Up Lamp Switch.........................25
Ballast Resistor..............................89
Battery..................................1,7,8
Blower Motor.............................68,70
Blower Resistors...........................68,70
Blower Switch............................68,70
Body Ground...............................44
Brake Warning Switch.........................67
Bulkhead Disconnect.................101,102,103,104
Camshaft Position Sensor.....................11,20
Cargo Lamp................................50
Center High Mounted Stop Lamp..................98
Charging System 2.5L..........................5
Generator.................................5